Human immune-deficiency Virus (HIV), the infectious agent that causes AIDS, has a complex structure. Here the capsid is surrounded by an additional covering called envelope. Glycoprotein’s present on the envelope enable the virus to bind to specific receptors on the surface of white blood cells of humans. Two identical RNA molecules are present inside the capsid and enzyme reverse transcriptase is associated with each RNA strand. As HIV is retrovirus, it has different type of multiplication.